Submitted by pwadmin on Fri, 2014-01-24 10:46
Here is a page describing how to remove duplicates in your system: http://book.civicrm.org/user/current/common-workflows/deduping-and-merging/
Email addresses are not unique in this system - an individual and an organization can both have the same email. It is a combination of name and email that makes a unique record. Sometimes a name is typed differently and will not match, for example, hyphenated surnames are sometimes written as two names without the hyphen.